The present invention is directed to an improvement in an optical film or strip waveguide which has a dielectric waveguiding layer applied on a substrate.
Since the radiation received from a supplying optical fiber generally has an unknown polarization, components for the optical communication technology in most applications should be polarization-independent. The propagation speed of a light guided in the component, however, is polarization-dependent in optical films or strip waveguides having a dielectric waveguide layer, and this, among other things, represents a problem for wavelength-selective components of integrated optics. In these waveguides, the TM-polarized light guided in the waveguiding layer has a higher propagation speed than a TE-polarized light guided in this layer. This difference in the propagation speeds for the TM- and TE- polarized light can be reduced by reducing the discontinuity in the refractive index between the waveguiding layer and its environment. However, in order to obtain an optical guiding waveguide layer at all, a finite discontinuity in a refractive index is necessary and, thus, a certain polarization-dependency of the effective refractive index of the waveguiding layer is also unavoidable.